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Texas Instruments SN74HC138PW
- Part No.:
- SN74HC138PW
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
SN74HC138PW.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,262
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Product details
Overview
SN74HC138PW from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in TSSOP-16 package, operating from 2 V to 6 V supply, with typical propagation delay of 15 ns at 6 V, ±4-mA output drive at 5 V, and active-low outputs enabling memory decoding and LED matrix column selection in industrial control systems.
For engineers reviewing the SN74HC138PW datasheet, SN74HC138PW pinout, SN74HC138PW application, or SN74HC138PW equivalent, this device serves as a high-speed, low-power logic decoder for memory address decoding, data routing, and LED display scanning where precise enable-controlled output activation is required.
Technical Context
The SN74HC138PW implements combinational logic decoding using three binary select inputs (A, B, C) and three enable terminals (G1, G2A, G2B), where one active-high (G1) and two active-low (G2A, G2B) enables allow cascading without external inverters. All eight outputs are active-low and mutually exclusive under valid enable conditions.
Its CMOS architecture ensures low static current (≤80 µA ICC), input leakage ≤1 µA, and compatibility with LSTTL loads-enabling direct interface with legacy logic families while maintaining rail-to-rail voltage operation across 2–6 V. Propagation delay varies with supply voltage, ranging from 38 ns (typ) at 6 V to 45 ns (typ) at 4.5 V per switching characteristics table.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 2 V to 6 V - supports mixed-voltage system interfacing and battery-powered designs down to 2 V logic levels. |
| Propagation Delay (tpd) | 15 ns (typ) at VCC = 6 V - enables use in high-speed memory decode paths where timing margin is critical. |
| Output Drive | ±4 mA at 5 V - sufficient to directly sink/source standard LSTTL inputs without buffering. |
| Input Leakage Current | ≤1 µA max - minimizes unintended biasing in high-impedance or floating-input configurations. |
| Quiescent Current (ICC) | 80 µA max - ensures ultra-low power consumption in always-on control logic stages. |
| Operating Temperature | –40 °C to +85 °C - qualified for industrial-grade embedded applications including factory automation and power infrastructure. |
Pinout & Package
TSSOP-16 package (5.00 mm × 4.40 mm body size), thin shrink small-outline package with exposed pad not present; lead finish NIPDAU/SN, RoHS compliant, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A) | Select input A (LSB) | Binary address bit 0; determines output selection when enables are asserted. |
| 2 (B) | Select input B | Binary address bit 1; combined with A and C to uniquely select one of eight outputs. |
| 3 (C) | Select input C (MSB) | Binary address bit 2; completes 3-bit decode word for Y0–Y7 mapping. |
| 4 (G2A) | Active-low enable A | First enable input; must be LOW for device operation; used for hierarchical decoding or data gating. |
| 5 (G2B) | Active-low enable B | Second enable input; both G2A and G2B must be LOW alongside G1 HIGH to activate outputs. |
| 6 (G1) | Active-high enable | Primary enable; must be HIGH to permit decoding; simplifies cascade logic with minimal external gates. |
| 7 (Y7) | Output 7 (MSB) | Active-low decoded output corresponding to ABC = 111; sinks current when selected. |
| 8 (GND) | Ground reference | Logic and power return path; requires low-inductance connection to minimize noise coupling. |
| 9 (Y6) | Output 6 | Active-low output for ABC = 110; shares same electrical specs and drive capability as Y0–Y7. |
| 10 (Y5) | Output 5 | Active-low output for ABC = 101; electrically identical to other Yx outputs with no internal differentiation. |
| 11 (Y4) | Output 4 | Active-low output for ABC = 100; designed for uniform fan-out and timing across all outputs. |
| 12 (Y3) | Output 3 | Active-low output for ABC = 011; maintains consistent VOL/VOL specs regardless of output index. |
| 13 (Y2) | Output 2 | Active-low output for ABC = 010; supports simultaneous multi-output driving within rated current limits. |
| 14 (Y1) | Output 1 | Active-low output for ABC = 001; compatible with LED cathode sinking in multiplexed displays. |
| 15 (Y0) | Output 0 (LSB) | Active-low output for ABC = 000; lowest-index output, commonly used as default or reset channel. |
| 16 (VCC) | Positive supply | Power rail for internal logic and output drivers; requires local 0.1-µF bypass capacitor per layout guidelines. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables hierarchical decoding up to 24 lines without external inverters, reducing board space and component count. |
| Active-low outputs | Directly interfaces with common-cathode LED matrices and NMOS/N-channel load switches without level-shifting. |
| Wide 2–6 V supply range | Supports interoperability across 3.3 V and 5 V systems, and extends battery life in 2.5–3.6 V portable applications. |
| Low 80-µA max ICC | Reduces system-level standby power in always-on controllers and remote sensors where quiescent current matters. |
| 15 ns typical tpd at 6 V | Meets timing budgets in fast memory subsystems where decoder delay contributes directly to effective access time. |
Applications
| LED Matrix Scanning | Memory Address Decoding |
|---|---|
Use Scenario: Driving columns of an 8×8 monochrome LED display using row/column multiplexing. IC Role / Device Role / Timing Role: Low-side column selector that activates exactly one Yx output at a time to sink current from illuminated LEDs. Use Value: Ensures only one column is enabled per cycle, preventing ghosting and reducing average current per LED while maintaining brightness via duty-cycle control. |
Use Scenario: Selecting one of eight SRAM or peripheral chips in a microcontroller-based industrial I/O module. IC Role / Device Role / Timing Role: Address-space partitioner translating upper address bits into chip-select signals for parallel memory expansion. Use Value: Minimizes added latency in memory access paths due to 15 ns typical propagation delay, preserving system timing margins. |
| Factory Automation I/O Expansion | Building Management System Logic |
Use Scenario: Expanding discrete digital outputs from a PLC controller to drive relays, solenoids, or indicator lamps. IC Role / Device Role / Timing Role: Output demultiplexer converting serial control bits into parallel actuator enable signals. Use Value: Provides galvanically isolated, current-sinking outputs capable of driving 4 mA loads directly-eliminating need for discrete transistor buffers. |
Use Scenario: Controlling HVAC zone valves, lighting circuits, or sensor multiplexing in smart building controllers. IC Role / Device Role / Timing Role: Logic-level signal router selecting between multiple analog sensor inputs or actuator command paths. Use Value: Operates reliably across –40 °C to +85 °C ambient, supporting deployment in unconditioned mechanical rooms and outdoor enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-to-8 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HC238PW | Active-high outputs; identical pinout and timing; requires inverted logic interpretation in firmware/hardware. | Suitable where downstream logic expects HIGH-active enables or LED anode driving instead of cathode sinking. | Select SN74HC238PW only if active-high output polarity aligns with system-level signal conventions and no level inversion is acceptable. |
| 74LV138PW | Lower 1.0–5.5 V supply range; faster 10.5 ns tpd at 3.3 V; higher ICC (160 µA max); different input thresholds. | Better suited for 3.3 V-only systems requiring tighter timing margins and lower voltage operation than HC family allows. | Choose 74LV138PW when operating strictly at 3.3 V with sub-12 ns delay requirements and higher power budget is acceptable. |
Compared with SN74HC138PW, SN74HC238PW offers identical form-factor and speed but inverted output polarity-requiring logic redesign-while 74LV138PW delivers superior speed at 3.3 V but sacrifices the 2 V minimum operating voltage and increases quiescent current nearly twofold.
Availability
SN74HC138PW is available at Aetrix Electronics and suitable for LED matrix displays, industrial memory decoding, and factory automation I/O expansion requiring stable component supply and long-term industrial temperature support.
Supply support for SN74HC138PW includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor leader focused on analog, embedded processing, and connectivity technologies, serving industrial, automotive, and communications markets with high-reliability components.
The SN74HC138PW belongs to TI's 74HC logic family, engineered for high-speed, low-power CMOS operation in industrial control, instrumentation, and memory interface applications where robustness and wide supply tolerance are essential.
FAQ
What is the maximum supply voltage rating for SN74HC138PW?
The absolute maximum supply voltage for SN74HC138PW is 7 V, but the recommended operating range is 2 V to 6 V per TI's SCLS107G datasheet. Operating above 6 V risks exceeding absolute maximum ratings and may cause permanent damage or parametric shift. Always observe the 6 V upper limit during normal operation.
Does SN74HC138PW support 3.3 V logic systems?
Yes, SN74HC138PW fully supports 3.3 V operation: VIH(min) = 2.0 V and VIL(max) = 1.0 V at VCC = 3.3 V per Section 6.3 of the datasheet, ensuring reliable recognition of standard 3.3 V CMOS logic levels. Its 2–6 V range makes it interoperable across mixed-voltage designs.
Can SN74HC138PW drive LEDs directly?
Yes, SN74HC138PW can drive LEDs directly in common-cathode configurations: each Yx output sinks up to 4 mA at 5 V (VOL ≤ 0.26 V), matching typical indicator LED forward currents. For higher-current LEDs, add external transistors-but for status indicators and low-brightness segments, direct drive is valid and widely implemented.
What is the thermal resistance (RθJA) of SN74HC138PW in its TSSOP package?
The junction-to-ambient thermal resistance RθJA for SN74HC138PW in TSSOP-16 is 141.6 °C/W per Section 6.4 of the datasheet. This value assumes standard JEDEC PCB mounting conditions; actual thermal performance improves significantly with copper pour and thermal vias beneath the package.
How does the enable logic work on SN74HC138PW?
SN74HC138PW requires G1 = HIGH, G2A = LOW, and G2B = LOW simultaneously to enable decoding. If any enable is violated, all Y0–Y7 outputs go HIGH (inactive). This three-input enable scheme allows flexible cascading-for example, using G1 as a system-level master enable and G2A/G2B for sub-block selection.
SN74HC138PW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 5.2mA, 5.2mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
SN74HC138PW FAQ
1.How can I place an order for SN74HC138PW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC138PW on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for SN74HC138PW reliable?
The price and inventory of SN74HC138PW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC138PW is usually 5 days.
3.What payment methods are accepted for SN74HC138PW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC138PW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC138PW?
SN74HC138PW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC138PW order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for SN74HC138PW?
For technical support, including SN74HC138PW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC138PW requirements.
6.How does Aetrix verify that SN74HC138PW is sourced from the original manufacturer or authorized distributors?
All SN74HC138PW products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74HC138PW meets industry standards.
7.What is the process for return or replacement of SN74HC138PW?
All SN74HC138PW units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC138PW, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The SN74HC138PW part is unused and in its original packaging.
Return procedure for SN74HC138PW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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